Maraging steels form a class of iron alloys. This group of materials has a martensitic crystal structure and is strengthened via aging at approximately 500 °C (900 °F), hence the portmanteau "maraging". These ultra-low carbon alloys have very high strength and hardness properties derived from precipitation of intermetallic compounds rather than carbon content. It is a material best used for tooling inserts and molds. This alloy is also called X3NiCoMoTi 18-9-5 or 1.2709.